Method of pulling strands of a cable into a conduit and associated system

Abstract

The invention provides a method for pulling strands or sub-groups of strands of a multi-strand cable into a conduit ( 3 ). In accordance with this method, a strand or sub-group of strands ( 2 ) to be pulled into the conduit is conveyed from one end of the conduit to the other by the movement of a drive element ( 1 ) in tension, to which the strand or sub-group of strands is temporarily coupled. In addition, the drive element in tension is designed not to enter a bundle of previously installed strands.

The invention claimed is: 
     
       1. A method for sequentially pulling strands or sub-groups of strands of a prestressing multi-strand cable inside a conduit, in which the strand or sub-group of strands to be pulled is conveyed from a first to a second end of the conduit and comes out at the second end by movement of a drive element in tension to which the strand or sub-group of strands to be pulled is temporarily coupled, the drive element in tension having a dimension chosen to prevent the drive element from entering a bundle of strands previously installed inside the conduit, the drive element also being pulled with the help of a first winch which is a haulage winch which allows an advance of the drive element placed at the second end of the conduit and connected to a second winch which is a braking winch which slows the advance of the drive element placed at the first end of the conduit, the drive element being tensioned by the traction exerted by the first winch and by a braking carried out by the second winch. 
     
     
       2. The method according to  claim 1 , in which the drive element in tension has sufficient dimensions and/or sufficient rigidity not to turn on itself or around the strand or sub-group of strands to be pulled. 
     
     
       3. The method according to  claim 1 , in which the drive element has a transverse dimension adapted depending on at least one of: a dimension of the conduit, a line of the conduit, a total number of strands of the multi-strand cable and a diameter of the strands. 
     
     
       4. The method according to  claim 1 , in which the drive element extends over the entire length of the conduit. 
     
     
       5. The method according to  claim 4 , in which the strand or sub-group of strands to be pulled is arranged relative to the drive element in tension on the same side as the bundle of previously installed strands. 
     
     
       6. The method according to  claim 1 , in which the strand or sub-group of strands to be pulled is temporarily coupled to the drive element by fastening to a shuttle fixed on the drive element. 
     
     
       7. The method according to  claim 6 , in which the shuttle is designed not to enter the bundle of previously installed strands. 
     
     
       8. The method according to  claim 1 , in which the conduit has a non-rectilinear line. 
     
     
       9. The method according to  claim 8 , in which the conduit comprises a portion having a curvature, of which the centre of curvature is situated lower than said portion of the conduit. 
     
     
       10. The method according to  claim 9 , in which the conduit comprises a portion having a substantially inverted U-shape. 
     
     
       11. The method according to  claim 1 , in which the drive element in tension has a substantially continuous and flat shape. 
     
     
       12. The method according to  claim 11 , in which the drive element comprises at least one belt. 
     
     
       13. The method according to  claim 1 , in which the drive element has a transverse dimension greater than 30% of a transverse dimension of the conduit. 
     
     
       14. The method according to  claim 13 , in which the drive element has a transverse dimension substantially equal to 60% of a transverse dimension of the conduit. 
     
     
       15. The method according to  claim 1 , in which, after pulling and uncoupling of said strand or sub-group of strands which remains inside the conduit, a following strand or sub-group of strands to be pulled is conveyed from the second to the first end of the conduit by movement of the drive element in tension to which the following strand or sub-group of strands to be pulled is temporarily coupled. 
     
     
       16. A system designed to implement a method for sequentially pulling strands or sub-groups of strands of prestressing multi-strand cable inside a conduit, the strand or sub-group of strands to be pulled is conveyed from a first to a second end of the conduit and comes out at the second end, the system comprising a drive element in tension suitable for conveying, by movement from a first to a second end of the conduit, a strand or sub-group of strands to be pulled that is temporarily coupled to it by coupling means, the drive element in tension having a dimension chosen to prevent the drive element from entering a bundle of strands previously installed inside the conduit, the drive element also being pulled with the help of a first winch which is a haulage winch which allows an advance of the drive element placed at the second end of the conduit and connected to a second winch which is a braking winch which slows the advance of the drive element placed at the first end of the conduit, the drive element being tensioned by the traction exerted by the first winch and by a braking carried out by the second winch. 
     
     
       17. The system according to  claim 16 , in which the drive element in tension has sufficient dimensions and/or sufficient rigidity not to turn on itself or around the strand or sub-group of strands to be pulled. 
     
     
       18. The system according to  claim 16 , in which the drive element has a transverse dimension adapted depending on at least one of: a dimension of the conduit, a line of the conduit, a total number of strands of the multi-strand cable and a diameter of the strands. 
     
     
       19. The system according to  claim 16 , in which the drive element extends over the entire length of the conduit. 
     
     
       20. The system according to  claim 19 , in which the strand or sub-group of strands to be pulled is arranged relative to the drive element in tension on the same side as the bundle of previously installed strands. 
     
     
       21. The system according to  claim 16 , in which the strand or sub-group of strands to be pulled is temporarily coupled to the drive element by fastening to a shuttle fixed on the drive element. 
     
     
       22. The system according to  claim 21 , in which the shuttle is designed not to enter the bundle of previously installed strands. 
     
     
       23. The system according to  claim 16 , in which the conduit has a non-rectilinear line. 
     
     
       24. The system according to  claim 23 , in which the conduit comprises a portion having a curvature, of which the centre of curvature is situated lower than said portion of the conduit. 
     
     
       25. The system according to  claim 24 , in which the conduit comprises a portion having a substantially inverted U-shape. 
     
     
       26. The system according to  claim 16 , in which the drive element in tension has a substantially continuous and flat shape. 
     
     
       27. The system according to  claim 26 , in which the drive element comprises at least one belt. 
     
     
       28. The system according to  claim 16 , in which the drive element has a transverse dimension greater than 30% of a transverse dimension of the conduit. 
     
     
       29. The system according to  claim 28 , in which the drive element has a transverse dimension substantially equal to 60% of a transverse dimension of the conduit. 
     
     
       30. The system according to  claim 16 , comprising means for, after pulling and uncoupling of said strand or sub-group of strands which remain inside the conduit, conveying a following strand or sub-group of strands to be pulled from the second to the first end of the conduit by movement of the drive element in tension to which the following strand or sub-group of strands to be pulled is temporarily coupled. 
     
     
       31. The system according to  claim 16 , further comprising a first winch placed at the second end of the conduit for pulling the drive element and a second winch placed at the first end of the conduit and to which the drive element is connected, the first winch and the second winch being arranged so that the drive element is tensioned by the traction exerted by the first winch and by a braking carried out by the second winch.